Low hone mineral density (BMD) and osteoporosis are significant problems facing the elderly, leading to 1.5 million fractures in 2002 (National Osteoporosis Foundation (NOF): America's bone health: The state of osteoporosis and low bone mass in our nation. Washington D.C., National Osteoporosis Foundation, 2002). Bisphosphonates, a class of compounds that generally inhibit the digestion of bone, have been used for over a decade to treat osteoporosis with significant success but cause unwanted side effects including osteonecrosis of the jaw, erosion of the esophagus, and atypical femoral fractures, which has lead to the reconsideration of the use of bisphosphonate therapy.
One alternative to treat osteoporosis has been the use of Whole Body Vibration (WBV), which consists of repeated mechanical loading of bone tissue through vibration devices, using, relatively high frequencies (e.g. 15-90 Hz) and relatively low mechanical loads (e.g. 0.1-1.5 g's). Studies have shown that WBV can delay and/or halt the progression of osteoporosis (Rubin et. al., Journal of Bone and Mineral Research, 19:343-351, 2004). In another randomized study, in which ≥0.6 g's of vibratory force were delivered to the feet of the patient, it was demonstrated that WBV was effective in improving hip BMD outcomes as compared to control groups that either did not exercise or were part of an exercise program (Verschueren et al., Journal of Bone and Mineral Research, 19:352-359, 2004).
Related studies have demonstrated the ability of WBV to improve hip and preserve spine BMD in populations of healthy cyclists, postmenopausal women and disabled children (Am J Phys Med Rehabil 2010; 89:997-1009, Ann Intern Med 2011; 155:668-679, J Bone and Mineral Research 2011; 26 (8):1759-1766).
The mechanism by which WBV influences BMD is an issue of some debate but studies have suggested that the shear stress within bone marrow in trabecular architecture during high frequency vibration could provide the mechanical signal to marrow cells that leads to bone anabolism (Journal of Biomechanics 45 (2012):2222-2229). More specifically, shear stress above 0.5 Pa is mechanostimulatory to osteoblasts, osteoclasts and mesenchymal stem cells (Journal of Biomechanics 45 (2012):2222-2229).
Many conventional methods of promoting bone tissue growth and bone maintenance by the application of WBV generally tend to apply relatively high frequency (e.g. 1.5-90 Hz) and relatively low magnitude mechanical loads (e.g. 0.1-1.5 g's) to bodily extremities, such as the use of vibrating platforms upon which a user stands that apply repeated mechanical loads to the feet of a user. Current WBV vibration platforms (e.g. Galileo 900/2000™, Novotec Medical, Pforzheim, Germany; or Power Plate™, Amsterdam, The Netherlands) and associated treatment regimens require the user to stand on a platform for up to 30 minutes a day, which is inconvenient for many users. Furthermore, applying vibration to the feet of the patient is an inefficient method for mechanically loading the hips, femur, and spine, the targeted areas for WBV therapy for osteoporosis. Up to 40% of vibration power is lost between the feet and the hips and spine due to mechanical damping in the knees and ankles (Rubin et al., Spine (Phila Pa. 1976), 28:2621-2627, 2003).
One other issue with current WBV platforms is the directionality of applied force. Standing on a vibrating platform, an individual receives WBV stimulus in a plane perpendicular to the spine and long bones of hip. Studies have shown that vibrations applied “in the inferior-superior direction would be misaligned with the principal trabecular orientation in the greater trochanter and femoral neck, resulting in lower shear. In contrast, trabeculae in the lumbar spine are aligned with the direction of vibration and the permeability is higher (Journal of Biomechanics 45 (2012):2222-2229).
There is a need for a more efficient and easy to use source of mechanical vibration that delivers 0.6 g+/−0.5 g of force directly to the spine and hips. A more efficient method for delivering vibration force would be to reduce the load applied to the patient and make the device easier to use, while maximizing therapeutic benefit to osteoporosis by localizing the repeated mechanical loads delivered to the hip and spine. Additionally, the potential to deliver WBV in a plane parallel to the directionality of the spine and long bones of the hip may be more beneficial than a traditional vibrating plate on which a person stands.
Finally, the existing technology of vibrating platforms limits the application of WBV to special populations that may benefit from its use. Cyclists, for example, have been shown to have lower BMD than other athletes and even lower than the BMD of sedentary people (Int J Sports Med 2012; 33:593-599). Thus, a wearable delivery system for this technology extends the reach of this tool to a wider population of individuals. Not only could a wearable device be used during cycling (or other activities), the present invention could be adapted to deliver WBV through a bicycle to the rider for the purpose of preserving BMD in cyclists.
In a separate but connected issue, WBV have been suggested to be “anabolic to the musculoskeletal system” and “in parallel, suppress adiposity” (PNAS. Nov. 6, 2007; 104 (45):17879-17884). In animal models, studies have shown that low magnitude WBV can reduce stem cell adipogenesis and can provide a tool for “nonpharmacologic prevention of obesity and its sequelae” (PNAS. Nov. 6, 2007; 104 (45):17879-17884). In a study done with obese women, WBV displayed a “positive effect on body weight and waist circumference reduction” (Korena J Fam Med. 2011; 32:399-405).